The present invention relates to a spray-on insulating material for building or, more particularly, to a material for building which is suitable for working to form a thick layer for heat and sound insulation on ceilings and walls by spraying thereto by use of a spray gun or blower gun as well as a method for the preparation of such a spray-on insulating material for building.
Needless to say, most of the modern buildings are provided with heat and sound insulating layers on the walls, ceilings and floors in order to enhance comfortableness of living as well as to save energies required for the temperature control of the building space. A wide variety of insulating materials are currently on use in accordance with the nature of the particular building and locality. For example, one of the most popular methods for heat and sound insulation in living houses is to apply a glasswool mat or a slab of cellular foamed plastic to the wall and the like.
These prior art materials for building insulation of heat and sound have their own respective disadvantages not only in the performance and workability in building construction but also in the expensiveness. In respect of the workability of the insulating material, there recently is a demand for a material suitable for forming a thick insulating layer on the ceiling or wall of a building ready-built or on the way of construction by the method of spraying with a spray gun.
Various kinds of such spray-on insulating materials for building are currently on the market. Most of these commercially available spray-on insulating materials are manufactured with cellulosic fibers as the base material. Unfortunately, none of them is quite satisfactory, in particular, in connection with insufficient non-inflammability or flame retardancy as an unavoidable consequence of the use of the organic fibrous material as well as the expensiveness. Therefore, there has been an eager desire to develop an inexpensive spray-on insulating material for building exhibiting excellent performance and workability.
Turning now to the problem of possible materials utilizable as a component of such a spray-on insulating material for building, it is an idea that, if an otherwise useless or rather noxious material such as an industrial waste material can be utilized and processed into such a building material, two-way advantages can be obtained in the disposal of the noxious waste material and in the commercial benefit with the production of useful building materials. Of course there have been made various attempts for the production of building materials by utilizing industrial waste materials but unfortunately there are known very few examples of commercial success.
The inventors have also continued extensive investigations for manufacturing a spray-on insulating material for building by utilizing industrial waste materials otherwise useless or rather noxious to cause environmental pollution and arrived at a conclusion that the gel-like aluminum hydroxide-containing sludge produced in large quantities in the aluminum processing industry is the most promising material for such a purpose.
To give an overview of the industries involving a serious problem of waste disposal to avoid environmental pollution, the works of aluminum fabrication are typically notorious due to the difficulties in the waste disposal. As is well known, aluminum articles in recent years are rarely used as shaped by extrusion, casting or other shaping means with the metallic aluminum surface exposed but almost always used after certain surface finishing.
The method of surface finishing of aluminum articles most widely undertaken in the aluminum industry is, of course, the surface anodization in which the surface of the aluminum article is electrolytically oxidized in an acidic electrolyte bath to be covered with a thin but dense layer of aluminum oxide and imparted with increased chemical and physical stability as well as beautifulness. A problem in the anodization treatment of aluminum articles is that a considerable amount of the aluminum metal is unavoidably dissolved both in the alkaline cleaning solution for degreasing before the anodization and in the acidic solution for anodizing electrolysis and the aluminum constituent thus contained in these solutions as well as in the washing water following the treatment is finally precipitated in the form of amorphous aluminum hydroxide when these solutions are mixed together and neutralized for sewage disposal.
The amorphous aluminum hydroxide thus precipitated usually forms a gel-like sludge containing considerable amounts of impurities coming from several steps of the aluminum fabrication such as sulfates, e.g. aluminum sulfate, aluminum hydroxysulfate, sodium sulfate and the like, and sodium aluminate. The gel-like aluminum hydroxide sludge contains large volumes, e.g. 70 to 90% by weight, of water but is hardly filtrable so that handling of such a material is extremely difficult. Therefore, the only way in the prior art for the disposal of such a gel-like aluminum hydroxide sludge is to discard it in a reclaimed land or in the ocean in the gel-like form as such.
Such a method of waste disposal is, of course, not quite acceptable even by setting aside the problem of the large cost for the transportation of such a waterish material to the reclaimed land or off to the ocean. For example, a reclaimed land filled with such a gel-like sludge is naturally weak in the yield strength of the ground resulting in a decreased utilizability of the land. Discarding of the sludge in the ocean is also not free from regulations to prevent pollution of water. Thus the waste disposal of the gel-like aluminum hydroxide sludge has been the most troublesome problem in the industry of aluminum fabrication.